1. Field of the Invention
The present invention relates to a display device including a liquid crystal display device and others, and particularly to a display device provided with a capacitance-type touch sensor that allows information input by a user's touch with his or her finger and others, and to an electronic unit provided therein with such a display device.
2. Description of the Related Art
A display device not using general pushbuttons as have previously been used for information input is recently receiving attention. Such a display device is exemplified by a liquid crystal display device, which is mounted directly thereon with a touch detection device generally called a touch panel. Hereinafter, such a touch detection device is referred to as touch sensor. On the display screen of the liquid crystal display device, various types of buttons are displayed for alternative use of the general pushbuttons. Considering the recent trend toward larger display screens of mobile units, this technology enables sharing of placement space between the display screen and the buttons, thereby indeed bringing the great advantages of space saving and a reduced number of components. However, such a technology has a problem of increasing the thickness of the liquid crystal module in its entirety due to the mounting of the touch sensor. Especially with the use in the mobile units, the touch sensor needs a protective layer for protection from scratches, whereby the liquid crystal module tends to be thicker than before. This is problematically against another trend toward
thickness reduction of the mobile units.
As examples, Japanese Unexamined Patent Application Publication No. 2008-9750 and U.S. Pat. No. 6,057,903 each describe a liquid crystal display element provided with a touch sensor, i.e., capacitance-type touch sensor, and make an attempt to reduce the thickness of the liquid crystal display element. In the capacitance-type touch sensor, a conductive film for touch sensor use is provided between a substrate and a polarizing plate of the liquid crystal display element. The substrate is the one placed on the viewing side of the liquid crystal display element, and the polarizing plate is the one placed on the outer surface thereof for viewing purpose. Between the conductive film for touch sensor use and the outer surface of the polarizing plate, the capacitance-type touch sensor is formed with a touch surface being the outer surface of the polarizing plate. As another example, Japanese Unexamined Patent Application Publication No. S56-500230 (published Japanese translation of a PCT application) describes the configuration in which a touch sensor is incorporated in a display device.